Field of the Invention
The present invention relates to an optical pickup device employed in the likes of a microscope.
Description of the Related Art
A knife edge method is known as one of focus detection methods of an optical pickup device employed in the likes of a microscope (for example, JP H7-129977 A). This knife edge method is a method in which a light intensity distribution of a light beam is found by dividing by the likes of a triangular prism a light beam reflected from a workpiece, and obtaining from this light intensity distribution information of a position (a focus position) of the workpiece with respect to a condensing position of an object lens.
However, although on the one hand this knife edge method has an advantage that a focus detection range is broad, in the knife edge method, when focus detection is performed on a workpiece of a transparent body of the likes of glass, it ends up that two reflection surfaces, that is, a surface and aback, are included in that focus detection range. Therefore, the knife edge method has a problem that focus detection signals generated by these two reflection surfaces end up being mixed and focus errors more easily occur.
The present invention was made in view of such a problem, and has an object of providing an optical pickup device achieving high precision focusing on a workpiece of a transparent body.